Tubing seal assemblies are available for permanent and retrievable seal bore packers and are designed to be used as a seal between the tubing string and packer. J-slot and straight slot seal assemblies consist of three major components: a J-slot or straight slot locator body, molded or premium seal units, and a mule shoe guide. The purpose of such conventional seal assemblies is to provide a reliable, fluid tight seal between the production tubing string and the well packer production bore. Such units use premium elastomer seal elements which can be redressed in the field. However, the use of such elastomer seals is limited by downhole conditions such as high temperature, high pressure and corrosive fluids. Such elastomer seal elements are subject to degradation because of operation at elevated temperatures, chemical attack, thermal expansion, mechanical rupture when undergoing compression set. Moreover, such seals do not have repeatable seal performance when it becomes necessary to pull the tubing string and thereafter reestablish the sealed connection.
The use of premium elastomer seals is limited because of the hostile environment in some deep wells, for example, where the geopressure may exceed 20,000 psi and the temperature may exceed 400 degrees F. Corrosive fluids, including hydrogen sulfide and manganese chloride, affect elastomer and rubber seals. Moreover, corrosion inhibitors may be injected in the well to protect the tubing string, and such corrosion inhibitors are known to attack and have a corrosive effect on elastomer seal materials. Such deep, hostile environments are typical for subsea well completions. It will be appreciated that because of the corrosive conditions, it may be necessary to retrieve the seal assembly for redress, which is an expensive undertaking, especially for subsea well completions.